Control of oxidation-reduction potentials in flavodoxin from Clostridium beijerinckii: the role of conformation changes.Ludwig, M.L., Pattridge, K.A., Metzger, A.L., Dixon, M.M., Eren, M., Feng, Y., Swenson, R.P.
(1997) Biochemistry 36: 1259-1280
- PubMed: 9063874
- DOI: 10.1021/bi962180o
- Primary Citation of Related Structures:
- PubMed Abstract:
- The Structure of Clostridium Mp Flavodoxin as a Function of Oxidation State, Some Comparisons of the Fmn-Binding Sites in Oxidized, Semiquinone and Reduced Forms
Ludwig, M.L.,Burnett, R.M.,Darling, G.D.,Jordan, S.R.,Kendall, D.S.,Smith, W.W.
(1976) FLAVINS AND FLAVOPROTEINS --: 393
- Structure of the Radical Form of Clostridial Flavodoxin: A New Molecular Model
Andersen, R.D.,Apgar, P.A.,Burnett, R.M.,Darling, G.D.,Lequesne, M.E.,Mayhew, S.G.,Ludwig, M.L.
(1972) Proc.Natl.Acad.Sci.USA 69: 3189
- Structure and Oxidation-Reduction Behavior of 1-Deaza-Fmn Flavodoxins: Modulation of Redox Potentials in Flavodoxins
Ludwig, M.L.,Schopfer, L.M.,Metzger, A.L.,Pattridge, K.A.,Massey, V.
(1990) Biochemistry 29: 10364
- The Structure of the Oxidized Form of Clostridial Flavodoxin at 1.9-A Resolution
Burnett, R.M.,Darling, G.D.,Kendall, D.S.,Lequesne, M.E.,Mayhew, S.G.,Smith, W.W.,Ludwig, M.L.
(1974) J.Biol.Chem. 249: 4383
- The Structure of a Clostridial Flavodoxin. I. Crystallographic Characterization of the Oxidized and Semiquinone Forms
Ludwig, M.L.,Andersen, R.D.,Mayhew, S.G.,Massey, V.
(1969) J.Biol.Chem. 244: 6047
- Cis-Trans Isomerization of the 57-58 Peptide in Crystalline Flavodoxins from C. Beijerinckii
Ludwig, M.L.,Dixon, M.M.,Pattridge, K.A.,Swenson, R.P.
(1994) Flavins and Flavoproteins 1993 : Proceedings of the Eleventh International Symposium, Nagoya (Japan) July 27-31, 1993 --: 363
- Structure of the Semiquinone Form of Flavodoxin from Clostridium Mp. Extension of 1.8 A Resolution and Some Comparisons with the Oxidized State
Smith, W.W.,Burnett, R.M.,Darling, G.D.,Ludwig, M.L.
(1977) J.Mol.Biol. 117: 195
- Structure and Redox Properties of Clostridial Flavodoxin
Ludwig, M.L.,Luschinsky, C.L.
(1992) Chemistry and Biochemistry of Flavoenzymes 3: 427
- Structural Characterization of Site Mutants of Clostridial Flavodoxin
Ludwig, M.L.,Pattridge, K.A.,Eren, M.,Swenson, R.P.
(1991) Flavins and Flavoproteins 1990 : Proceedings of the Tenth International Symposium, Como, Italy, July 15-20, 1990 --: 423
X-ray analyses of wild-type and mutant flavodoxins from Clostridium beijerinckii show that the conformation of the peptide Gly57-Asp58, in a bend near the isoalloxazine ring of FMN, is correlated with the oxidation state of the FMN prosthetic group. ...
X-ray analyses of wild-type and mutant flavodoxins from Clostridium beijerinckii show that the conformation of the peptide Gly57-Asp58, in a bend near the isoalloxazine ring of FMN, is correlated with the oxidation state of the FMN prosthetic group. The Gly-Asp peptide may adopt any of three conformations: trans O-up, in which the carbonyl oxygen of Gly57 (O57) points toward the flavin ring; trans O-down, in which O57 points away from the flavin; and cis O-down. Interconversions among these conformers that are linked to oxidation-reduction of the flavin can modulate the redox potentials of bound FMN. In the semiquinone and reduced forms of the protein, the Gly57-Asp58 peptide adopts the trans O-up conformation and accepts a hydrogen bond from the flavin N5H [Smith, W. W., Burnett, R. M., Darling, G. D., & Ludwig, M. L. (1977) J. Mol. Biol. 117, 195-225; Ludwig, M. L., & Luschinsky, C. L. (1992) in Chemistry and Biochemistry of Flavoenzymes III (Müller, F., Ed.) pp 427-466, CRC Press, Boca Raton, FL]. Analyses reported in this paper confirm that, in crystals of wild-type oxidized C. beijerinckii flavodoxin, the Gly57-Asp58 peptide adopts the O-down orientation and isomerizes to the cis conformation. This cis form is preferentially stabilized in the crystals by intermolecular hydrogen bonding to Asn137. Structures for the mutant Asn137Ala indicate that a mixture of all three conformers, mostly O-down, exists in oxidized C. beijerinckii flavodoxin in the absence of intermolecular hydrogen bonds. Redox potentials have been manipulated by substitutions that alter the conformational energies of the bend at 56M-G-D-E. The mutation Asp58Pro was constructed to study a case where energies for cis-trans conversion would be different from that of wild type. Intermolecular interactions with Asn137 are precluded in the crystal, yet Gly57-Pro58 is cis, and O-down, when the flavin is oxidized. Reduction of the flavin induces rearrangement to the trans O-up conformation. Redox potential shifts reflect the altered energies associated with the peptide rearrangement; E(ox/sq) decreases by approximately 60 mV (1.3 kcal/mol). Further, the results of mutation of Gly57 agree with predictions that a side chain at residue 57 should make addition of the first electron more difficult, by raising the energy of the O-up conformer that forms when the flavin is reduced to its semiquinone state. The ox/sq potentials in the mutants Gly57Ala, Gly57Asn, and Gly57Asp are all decreased by approximately 60 mV (1.3 kcal/mol). Introduction of the beta-branched threonine side chain at position 57 has much larger effects on the conformations and potentials. The Thr57-Asp58 peptide adopts a trans O-down conformation when the flavin is oxidized; upon reduction to the semiquinone, the 57-58 peptide rotates to a trans O-up conformation resembling that found in the wild-type protein. Changes in FMN-protein interactions and in conformational equilibria in G57T combine to decrease the redox potential for the ox/sq equilibrium by 180 mV (+4.0 kcal/mol) and to increase the sq/hq potential by 80 mV (-1.7 kcal/mol). A thermodynamic scheme is introduced as a framework for rationalizing the properties of wild-type flavodoxin and the effects of the mutations.
Department of Biological Chemistry, University of Michigan, Ann Arbor 48109-1055, USA.